@insomniac7809 So let's use a specific scenario from a Wheel of Time setting as an example case of how these principles should be applied.
In that universe there are two closely allied factions: Aes Sedai and Warders. The former are witches who are literally unable to use their magic to harm anyone other than the Big Bad's servants, and the latter are elite warriors acting as their bodyguards.
Therefore what theoretically keeps Aes Sedai in check are social reasons (mobs with pitchforks - the superstitious populace will turn against usage of magic), magical (their power won't work against regular people) and other enemy factions who'd love to burn dem witches.
In practice as was mentioned earlier in the thread players skirted the lines fairly regularly:
- Aes Sedai PCs used loopholes they didn't in the books. "I can't burn you alive but I can immobilize and gut you with this here sword", "I'll use magic to throw a boulder at your head, how's that?"
- Skewed demographics: The prevalence of magic users weakened anti-magic user factions who should have been far more populous, but which in practice was never the case on the grid.
- This all weakened Warders' niche as bodyguards.
Balancing the reality of the game versus the atmosphere we wanted based on the book series the setting was derived from was a common debate.